Since I've had the car and phone, both have been used pretty much every day.
Battery Life: I charge my phone every night since its by my bed side, so I cant tell you if there is an enormous power draw from the BT. I know that the E815's battery life isnt that great through. Without the car, itll last for 2 days with moderate use and then start beeping for 6 hours before it cuts off.
Glitches: I havent found any. The closest thing to a glitch is the annoyance of being of the phone while getting into the car. It takes iDrive about 5 to 10 seconds to connect the audio from the phone to the car. During this time, you and the person you are talking to are cut off from each other. I've just gotten in the habbit of saying hold on as I turn on the car, as if I have to do something else to allow for a smooth transition
I also have a 12 volt car charger for the phone, and if I'm going on a long trip, I might plug it into that instead of dragging my home charger along.
06' BMW 330i & 03' Suzuki GSX-R600
SG | Beige Dakota | Poplar || iDrive w/MP3 | PP | SP | CWP | PDC | Comfort | Shades || 40% Tint | Black Line Tail Lights | Hardwired V1